Abstract:

Little is known about the effects of arabinoxylans (AX) on noodle quality. The aim of
this study was to observe interrelationships between wheat flour AX, SRC tests, and
noodle quality attributes, and to investigate the use of SRCs to predict cookie diameter.
Cookie diameter is the most common index of overall soft wheat quality used in
practice. Duplicate samples of 63 soft white wheat (Triticum aestivum) varieties and
breeding lines grown at Corvallis in 2002 were selected to study the relationships
between flour and noodle characteristics. Kernel hardness was positively correlated
with starch damage, total AX and water-extractable AX (WEAX) content but
negatively correlated with break flour yield. In this set of samples, despite significant
correlations, the sodium carbonate and sucrose SRC tests were not considered to be
reliable predictors of cookie diameter due to low numerical correlation coefficients.
A modified extraction method for WEAX-SE and WUAX-SE was optimized and
reduced in scale. During method development, WUAX 1-SE and WUAX 2-SE
fractions that had been treated with protease and amylase respectively were observed
using SEHPLC. The equivalent fractions had been discarded in other studies. In this study, AX was found to present in these fractions. A subset of 12 lines was used for
further AX extraction. WUAX 2-SE had the highest molecular weight, followed by
WUAX1-SE, and then WEAX-SE. The molecular weights of WEAX-SE ranged from
approximately 411,305 and 447,282. However, molecular weight of WUAX 1-SE and
WUAX 2-SE could not be specifically defined in this study. In addition, WEAX-SE
contained a higher degree of substitution than WUAX 1-SE and WUAX 2-SE.
For the whole sample set, flour protein content was negatively correlated with ti5A
cooked noodle hardness, adhesiveness and chewiness but positively correlated with
springiness. At the very low flour protein contents of this sample set, protein
composition, which related to lactic acid SRC, became more important for noodle
texture. Both starch damage and sodium carbonate SRC were positively correlated
with cooked noodle hardness and chewiness at t₀ and t [subscript 15A] Total AX and WUAX were
positively correlated with adhesiveness at to, which might result from gummy and
sticky characteristics of AX.
Using the subset of 12 lines, described above, increased xylose and arabinose contents
reflected overall higher AX abundance, and were related to harder kernel texture, poor
milling properties. They were also related to higher water, carbonate and sucrose
SRCs, and smaller cookie diameter. A/X ratios of WEAX-SE and WUAX 1-SE were
positively correlated with flour yield and break flour yield. The WUAX 2-SE fraction
seemed to behave different from the WEAX-SE and WUAX 1-SE fractions. The
relationships between A/G ratio, and milling characteristics and SRC were opposite to A/X ratios for all fractions. Decreased MW and increased abundance of WUAX in this
sample set was related to poorer milling characteristics. There appeared to be no direct
systematic relationships between AX and cooked noodle texture parameters in this
study. However, AX content appeared to affect noodle texture indirectly, mediated
through the effects ofAX on kernel hardness, milling properties, starch damage,
reduced FSV, and hence harder noodle texture. Kernel hardness index, flour yield,
break flour yield and tisw cooked noodle hardness were able to be predicted with some
confidence using stepwise multiple regressions that used selected parameters from the
WEAX, WUAX 1-SE and WUAX 2-SE fractions.